The present invention relates to a system and method for conditioning the pelvic musculature using one or more implanted microstimulators, and more particularly to a system and method for treating urinary incontinence using a radio-frequency-controlled implanted microstimulator.
Urinary incontinence is an enormous medical and social problem, affecting 8% of people in industrialized countries. Expenditures on its treatment are conservatively estimated to be over 10 billion dollars. Nevertheless, aggressive therapies for this condition are used to treat only a small part of the affected population, and much of the market is driven by the need for absorptive products rather than state-of-the-art devices.
Incontinence can be divided into at least three major categories of pathophysiology:
1. Overflow incontinence, which arises from a failure of the bladder to contract at all or adequately for substantial emptying, so that urine accumulates until it overflows. This commonly occurs in spinal cord injury. PA1 2. Stress incontinence, which arises from weakness of the urethral sphincteric muscles, which are unable to stop the forceful expulsion of urine during transient increases in intra-abdominal pressure such as during coughing and lifting. This commonly occurs in women following childbirth and/or menopause. PA1 3. Urge incontinence, which arises from spontaneous activity of the bladder and/or sphincteric muscles producing a compelling feeling that the bladder needs to be emptied even when it contains little urine. This afflicts both men and women and probably arises from a variety of poorly understood dysfunctional reflexes.
It is has been observed over the past 50 years or so that conditioning exercises of the pelvic musculature can produce a reduction of stress incontinence in a majority of women who undertake this treatment. Pelvic conditioning therapies could potentially assist a large proportion of the more than 6 million women affected by stress incontinence in the United States alone. However, such exercises have not proved easy for many women to perform by voluntary contraction of the relevant muscles. Thus, electrical stimulation has been used to force contraction of the relevant muscles, and thereby achieve the desired muscle conditioning exercises.
Prior art devices that provide electrical stimulation to condition the pelvic musculature are based on the use of transcutaneous electrical stimulators which exercise pelvic muscles using externally-controlled regimes. While these prior art transcutaneous devices, introduced into the vagina or anal canal, have proven to be effective, they are often disliked by patients because of the associated embarrassment and sanitary problems. Further, in addition to stimulating the motor nerves, transcutaneously applied electrical currents necessarily stimulate the sensory nerves of the overlying skin, producing unpleasant sensations. It is thus apparent that there is a need in the art for a system and/or method for achieving the benefits of electrical stimulation of the pelvic musculature without the attendant problems associated with transcutaneous devices.
Stimulation of the bladder, sphincter and/or adjacent pelvic musculature and cutaneous nerves may also cause a reduction in the spontaneous sensations and contractions associated with urge incontinence, which is often combined with stress incontinence. The neural mechanism is unclear, but is believed to relate to a general property of neural reflect pathways that they can drift into states of hypersensitivity or spasticity as a result of various nonspecific insults and dysfunctional patterns of usage. Electrical stimulation may give rise to inhibitory neural activity that breaks the cycle of spasticity during a particular bout of urge incontinence. Repeated application of such stimulation may permit the patient to resist inappropriate urges to empty the bladder, thereby rebuilding normal bladder capacity and reducing the frequency of sensation that the bladder needs to be emptied. Repeated electrical stimulation may also lead to a reduction in the hypersensitivity of the neural pathways responsible for spontaneous sensations and contractions and a concomitant reduction in the incidence and/or severity of bouts of urge incontinence. Hence, it is evident that improved methods and techniques for electrically stimulating the bladder, sphincter and/or adjacent pelvic musculature and cutaneous nerves is socially and medically desirable, and would produce enormous benefits for patients suffering from incontinence, particularly stress incontinence and urge incontinence.
In U.S. Pat. No. 5,199,430, issued to Creasey et al., there is disclosed an electrical assistive device and a method for electrical stimulation that is used to produce urination in patients who have lost voluntary control of the bladder (such as the overflow incontinence pattern described above).
In U.S. Pat. No. 4,739,764, issued to Gleason et al., a method is described for controlling bladder emptying through the electrical stimulation of peripheral nerves supplying the bladder wall and external urethral sphincter. The method disclosed by Gleason et al. includes two applications related to urinary dysfunction. First, the method is suggested to assist bladder emptying for patients who have lost the ability to urinate under volitional control. Second, the method is suggested to assist the patient who is incontinent by providing a means to stimulate the sphincter muscles electrically. Specifically, the method described stimulates identified nerve bundles by using epineural electrodes, and by providing moment-to-moment control of the urinary sphincter at the time that continence is sensed to be compromised. This differs from the approach taken by Applicants in the present application in that Applicants' invention stimulates using small implantable stimulators that are implanted in or near the pelvic floor muscles for the purpose of providing conditioning stimulation on a regular, ongoing schedule. Such ongoing conditioning then results in continence via the natural voluntary control available to the patient. In other words, while the '764 patent addresses the continence problem by attempting to control the urinary sphincter with electrical stimulation, the present invention addresses the continence problem by regularly conditioning the pelvic muscles with electrical stimulation so as to restore voluntary control to the patient.